Microlens and lenticular lens sheets are elements to be used in a back-light unit of a liquid crystal display, a rear-projection display, a projection screen, a stereoscopic display, and the like. In general, a convex lens is formed as a dot or a stripe on a surface of a transparent substrate such as glass or a plastic sheet.
In particular, a three-dimensional display is known as one of the display systems which have at attention as next-generation display systems. Among modes of three-dimensional display, as one which does not require any special glasses, a lenticular mode is typically given (Non Patent Literature 1). Various three-dimensional displays of such mode in combination with a flat panel display such as a liquid crystal display (LCD) have recently been proposed, and thus the mode is considered to be closest to a practical level. However, in the conventional lenticular mode, an image resolution depends on a pitch of a lens or a barrier. Hence, a lens having a higher definition is required for realizing a display having a higher resolution. Further, it is necessary to position a lens and a barrier accurately with respect to a flat panel display.
Meanwhile, a three dimensional display using a field-sequential light direction control back light has recently been proposed as a novel mode of the three-dimensional display (Patent Literature 1). A principle of this mode involves adopting, as a back light of a display, a field-sequential light direction control back light 1 which can change a direction of light (LD) from the back light sequentially at high speed through use of a lenticular lens, and displaying an image depending on the direction of the light on a transmission display 2. Through utilization of this, binocular parallax images are provided in directions of left and right eyes (LE and RE), and the directions are switched at blinding speed, thereby being able to give a three-dimensional image to an observer. Further, an image resolution of this mode is the same as that of an LCD, and hence a high resolution of the LCD can be directly utilize, which facilitates manufacture and an increase in resolution.
Meanwhile, the lenticular lens has a spherical surface profile, and the following methods have hitherto been adopted as processing means therefor. That is, for example, there are given: (1) subjecting a molten or semi-molten thermoplastic resin to injection molding; (2) subjecting a sheet to embossing under heating (see Patent Literature 2); (3) curing an ultraviolet curable resin in a template with ultraviolet light (see Patent Literature 3); and (4) subjecting an ultraviolet curable resin to screen printing, and curing the ultraviolet curable resin with ultraviolet light (see Patent Literature 4). However, it can be said that each of those methods is a manufacturing method involving the following drawbacks. The manufacturing method requires a mold having high processing accuracy or requires a printing plate. Further, the mold circa plate inevitably comes into contact with a lens surface, and hence it is difficult to eliminate a risk of contamination with foreign matter, and moreover, a flaw in the mold or the like is reflected.
Meanwhile, there has been proposed a method of forming a microlens through use of inkjet or the like (Patent Literature 5). That is, the patent literature relates to a method of forming hemispherical specular dots for preventing incident light from diffusing or scattering, in manufacturing, for example, a light guide plate of a back light to be used in a liquid crystal display apparatus, on one surface or both surfaces of a plastic to serve as a base material for the light guide plate. This method has an advantage in that there is no need to produce a mold, as compared to the manufacturing method using injection molding processing or the like as describe above. In the case of this method, however, a polycarbonate resin or the like to be used as the base material has high surface energy, and hence is highly compatible with a microlens formation material for forming specular dots. Thus, a microlens to be formed undergoes planarization, possibly resulting in a reduction in luminance. In actuality, Patent Literature 5 has no description about a material composition suitable for a profile of the microlens.
It should be noted that Patent Literatures 6 and 7 disclose to soluble polyfunctional vinyl aromatic copolymer obtained by polymerization of a divinyl aromatic compound (a) and a monovinyl aromatic compound (b) in an organic solvent in the presence of a Lewis acid catalyst and an initiator having a specific structure at a temperature of 20 to 100° C. In addition, the soluble polyfunctional vinyl aromatic copolymer is excellent in solvent solubility and processability, and can be used to yield a cured product excellent in heat resistance and thermal decomposition resistance. Further, Patent Literature 8 describes that the copolymer is a material suitable for an optical material. However, there is no attempt to apply the copolymer to an inkjet process in any of the literatures.